In general you'll get better pictures with a great lens and an average body/sensor than with an average lens and a great body/sensor.

Just how much the balance needs to be between the two can be highly dependent upon what kind of subject matter you're photographing, what the lighting conditions are, do you get multiple opportunities to get the shot or is it a decisive moment that happens and is gone in the blink of an eye, how large you plan on displaying the image, etc. There's a big difference between shooting landscapes in early morning or late afternoon from a tripod mounted camera for use as a bus stop ad and shooting sports under artificial lighting while handholding the camera for web distribution.

Different shooting scenarios require different minimum capabilities from the camera body in terms of multiple things such as frame rate, low light/high ISO sensitivity, image resolution (megapixels), dynamic range (the difference between the brightest and dimmest details the sensor can record at the same time), and autofocus capability in terms of speed, accuracy, and consistency. Some subjects are almost always manually focused so the camera's AF performance is not a factor at all. For other subjects AF is critical for most photographers to be able to get the shot.

Newer cameras offer features that do more of the work for photographers than older cameras do, especially in the areas of autofocus and exposure calculation. They also provide more instant feedback even before the image is captured using exposure preview and showing what parts of the scene are in focus in an electronic viewfinder. Most of these newer and/or more accurate capabilities benefit beginning photographers more than seasoned photographers who learned long ago how to get challenging shots without all of the new capabilities packed into cameras todays.

Having said that, if your body and sensor are older and well below current standards even an exceptional lens won't help you if you have a need to shoot in very low light at ISO 12800 and the camera only goes to ISO 3200 or you need to be able to burst at 20+ frames per second and the camera can only do 5 fps.

Lenses are what capture and focus light. Cameras just record what the lens has refracted. My advice is to get a modestly priced camera that barely meets the requirements for what you wish to shoot and then buy the best lenses you actually need that you can afford. Don't think you need 5-6 different lenses to "cover all of the bases". You'll wind up spending money on some you hardly ever use. Instead, get a few lenses that actually do what you need them to do to get the kinds of shots you want to get.

I've been shooting a long time and have several lenses I should have sold years ago because I never use them. I shoot 95% of what I do with only four different lenses (two zooms and two primes) on two different bodies, and the next 4.9% with only 2-3 more lenses (2 primes and one wide angle zoom that I use more like a prime at its widest FL) and one additional body.